Binder and surface coating made from coal and asphalt



M. D. SCHLESINGER ETAL 3,264,957

Aug. 9, 1966 BINDER AND SURFACE COATING MADE FROM COAL AND ASPHALT Filed Jan. 18; 1963 2 Sheets-Sheet 1 FIG. I.

INVENTOR MART/N D. .S'GHLESl/VGE'R RA YMOND W. H! TE SI-IUE 1966 M. D. SCHLESINGER ETAL 3,264,957

BINDER AND SURFACE COATING MADE FROM COAL AND ASPHALT Filed Jan. 18, 1963 2 Sheets-Sheet 2 IN VENT 0R5 Martin D. Schlesinger Raymond W. Hiteshue coal in petroleum asphalt.

United States Patent 3,264,957 BINDER AND SURFACE COATING MADE FROM COAL AND ASPHALT Martin D. Schlesinger and Raymond W. Hiteshue, Pittsburgh, Pa., assignors to the United States of America as represented by the Secretary of the Interior Filed Jan. 18, 1963, Ser. No. 252,534 11 Claims. (Cl. 94-9) The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention is concerned with a composition for use as a binder and surface coating material and a method for preparation of the composition.

Present day large road building programs and mainte nance of extensive systems of highways creates a demand for asphaltic binders and surface coatings which may in many areas exceed the supply. It is, accordingly, an object of the present invention to provide a method and product which will decrease the quantities of asphaltic materials necessary for preparation of such binders and surface coatings.

It has now been found that this object may be achieved by means of a process comprising digestion of bituminous According to the process of the invention a mixture of coal and asphalt is heated to a temperature of from about 250 to 450 C. for a period of from about /2 to about 4 hours. During this digestion the particles of coal are partially dissolved and the balance is stably dispersed throughout the product and a homogenous product is formed.

The digestion time is not critical; however, sufficient time should be allowed for the particles of coal to come to reaction temperature, the volatile matter to evolve from the coal particles and asphalt to penetrate into the re maining coal structure. The product has been found to be of particular value as a binder for road building aggregates consisting of mixed sizes of stone or slag.

Since amounts of coal as high as or higher may be added to the asphalt, the process of the invention results in a substantial extension of available asphalt while at the same time making use of a very plentiful and relatively inexpensive material, bituminous coal. In addition, the product of the invention has been found to be equal in quality and in some cases superior to the asphalt alone as will be indicated in the examples which follow. The economies possible as a result of the invention are apparent from a consideration of the cost of bituminous coal, about $6.00 per ton, and petroleum asphalt at $16.00 per ton.

It has been found that the preparation of a satisfactory product requires a reaction between the coal and asphalt at elevated temperature. Mere mixing or mild heating (to decrease the viscosity of the asphalt) is not sufficient since bituminous coal is insoluble in petroleum asphalt. The exact nature of the reaction is not known but appears to involve devolatilization of the coal with the products of devolatilization subsequently combining with k the asphalt.

For further objects and advantages, reference is had to the following drawings in which:

FIG. 1 illustrates a digestion apparatus suitable for preparation of the composition of the invention.

FIG. 2 is a cross-section of a multi-layer road made from the composition of the present invention.

The following example will serve to more particularly describe the invention.

A high volatile bituminous ,A coal is crushed and .ground to a particle size of about 80% finer than 200 3,264,957 Patented August 9, 1966 mesh. 0.52 pound of coal and 2.08 pounds of -100 penetration grade air blown asphalt from midcontinent crude oil are circulated through a steam heated (130 C.) Viking gear pump for three hours to provide an even distribution of coal particles throughout the asphalt. The mixture is then transferred to the autoclave portion of a digestion unit of the type illustrated in the FIGURE 1. The digestion unit consists of an externally heated autoclave 1, the top of which is closed by means of adapter head 2. The adapter head is provided with inlet for N gas 3, stirrer 4, thermocouple well 5 and a vapor exhaust 6. The latter connects by means of ground glass joint 7 to air condenser 8 and by means of a second ground glass joint 9 to separatory funnel 10.

The digester is initially purged with nitrogen gas to remove air from the system since the air and hydrocarbon vapors formed during digestion could form an explosive mixture. The digester is then heated externally to 315 C. as measured by a thermocouple (not shown in drawing) and the mixture of coal and asphalt maintained at this temperature with stirring for a period of one hour. Vapors produced during the digestion are condensed and accumulated in the separatory funnel. Condensed liquids are returned to the digestion vessel at the end of the digestion period while the system is cooling to room temperature and are mixed (by stirring) with the digested coal-asphalt mixture. Air condenser 8 is replaced by a reflux air condenser not shown in drawing) during the cooling period.

The final product is stable and may be stored in containers until ready for use. Tests made on the product prepared according to the above procedure indicate that products containing up to at least 20 weight percent coal have properties suitable for binding aggregates. The maximum percentage of coal which may be used will depend on the nature of the coal and asphalt as well as the reaction conditions; however, amounts substantially in excess of 20% generally tend to result in a product which is too brittle and will crack under the stress of traffic, especially'in wintertime. Results of the tests are summarized in the following table:

TAB LE 1 Preparation:

Coal, weight-percent 0 Asphalt, weight-percent Mixing:

Time, hours Temperature, C...

Digestion:

Time, hours Temperature, C

Product analysis: Penetration, mm.X10-

77 88 89 Ductility, cm 37-65 25-40 Settling test, wt.-pct:

Insolubles in top. 9. 0 13. 8 Insolubles in bottom 9. 2 25. 6 Softening point, G 51 47 Compressive strength, p.s.i., maxi- 240 219 207 Benzene in solubles, wt.-pct 0.02 1 8.9 17. 7

1 30 hours at C. 1 From test on 4-inch briquet prepared with 90% aggregate.

It will be noted that penetration of the finished product was actually higher than the starting material indicating that the process of the invention yields a product of suitable workability. Penetration, as well as ductility, are also indicative of the ability of a road to retain a limited range of pliability in winter and summer.

The settling test consisted of treatment of the product in an open oven at 105 C. for thirty hours. Samples were then taken from the top and bottom of the container and analyzed for insoluble content. Benzene extraction and weighing of the residues showed that the insoluble content from top and bottom was the same in the case of the 10 percent coal binder. Thus, the stability of the dispersion was .demonstrated and no separation would be anticipated during prolonged storage at ambient temperatures or during the paving mix operation. Partial settling was indicated in'the single test of the 20% coal binder, but even this binder would be considered adequately stable for use as a road surface.

In order to evaluate the products under conditions of actual use, field tests were run using binders prepared as described above for road construction. A section of roadway was laid consisting of three sectionsthe first was a control employing asphalt alone as binder, the second employed the coal-asphalt product of the invention containing 10 weight percent coal as binder, and the third employed the coal-asphalt product of the invention containing 20 weight percent coal as binder. Compositions of the base and wearing courses and paving conditions are given in the following table:

TAB LE 2 era- Base course and wearing course are standard terms used in road construction. As shown in FIG. 2, the base course 11 contains relatively large sized aggregate and is the load bearing section of the road. It is placed on the prepared sub-base 12 of large stones, slag or stabilized soil. The wearing course 13, placed on the base course, forms the surface of the road and provides the traction and smooth riding qualities of the road. The aggregate of the base course was crushed slag consisting of a mixture of particles of 1.5 inch to 8 mesh size; that of the wearing course was crushed slag consisting of a mixture of particles of 4 to 100 mesh size.

Both courses were mixed, poured and rolled hot according to state highway specifications (Commonwealth of Pennsylvania, Department of Highways, Bulletin 27, 1954). Temperature measurements of the paving mixture during preparation and application are shown in Table 2. These experimental roadway sections were used for over a year under a daily tralfic load of cars and trucks of about 300 vehicles and showed no signs of deterioration at the end of the period.

It will be apparent that the addition of as much as 20% of coal to the asphalt results in a substantial savings in the amounts of asphalt required in road building. Furthermore, the process of the invention provides a valuable use for bituminous coal which is available in plentiful and economical supply in many areas. These desirable objectives are achieved without loss of the desirable properties of asphalt such as penetration, adhesion and resistance to weathering. In fact, as illustrated above as regards penetration, the desirable properties may actually be increased.

The product can be used for road building in the same manner as asphalt is presently employed, i.e., the same mixing and application equipment may be used and operated at the same temperature.

The apparatus employed in preparation of the product may, of course, be varied Widely provided only that it is sufiicient to provide necessary elevated temperature and mixing of the coal and asphalt.

Though a temperature of 315 C. as employed in the example, has been found to give very satisfactory results, the temperature may be varied over a wide range provided it is sufficient to ensure reaction between the coal and asphalt. A temperature range of about 250 to 400 4 -C. is generally satisfactory; however, a temperature as high as 450 C. may be satisfactory with asphalts which are more resistant to decomposition at high temperature. Some asphalts will, however, decompose at temperatures above 400 C. resulting in a product which is fluid and unsuitable for roadbuilding.

The time of the reaction may also vary considerably depending on the temperature employed, state of subdivision of the coal, etc. Again, the only essential criterion is that the time be sufficient to allow reaction to take place resulting in the maximum dissolution of the coal in the asphalt.

The composition of the coal and asphalt may also be varied over a considerable range,.i.e., several coals or asphalt from different types of petroleum, provided only that the coal is bituminous and the asphalt is of petroleum origin. Optimum particle size of the coal may also vary considerably depending on reaction conditions and the asphalt employed; however, the particle size must be small enough to ensure reaction with the asphalt. A particle size of 200 mesh or finer obtained by grinding in a ball mill, has been found to be most satisfactory.

The use of the product is not restricted to road building material but may be employed in a wide variety of uses, particularly where a waterproof or vaporproof barrier is required, for example, as a filler material in building components. Typical uses would include materials of construction such as impregnated panels and shingles.

What is claimed is:

1. A road surface comprising a base course, about 1.5 to 2.0 inches in thickness, and a wearing course, about 0.5 inch in thickness; both of said courses comprising a composition consisting of (a) an aggregate from the group consisting of crushed stone and crushed slag and (b) a binder prepared by a method comprising intimately mixing petroleum asphalt and up to about 20 percent of finely divided bituminous coal and digesting the mixture at a temperature of from about 250 C. to about 450 C. for a period of time sufiicient to ensure reaction of the coal with the asphalt and maximum dissolution of the particles of coal in the asphalt.

2. The road surface of claim 1 in which the binder comprises about 9 percent of the base course and about 9 percent of the wearing course.

3. The road surface of claim 1 in which the particle size of the aggregate in the base course is from about 8 mesh to about 1.5 inches and the particle size of the aggregate in the wearing course is from about 4 mesh to about 100 mesh size.

4. A method for preparing a binder and surface coating material composed of an insoluble particulate bituminous coal residue dispersed in a solution of bituminous coal constituents and petroleum asphalt comprising (a) intimately mixing petroleum asphalt with a finely divided bituminous coal, the coal being added in an amount up to about 20% by weight of the total mixture;

(b) heating the mixture at a temperature of from about 250 C. to about 450 C. for from about /2 hour to about 4 hours, thereby forming a dispersion of insoluble bituminous coal residue in a solution composed of (1) the. petroleum asphalt and (2) constituents of the bituminous coal.

5. Method of claim 4 in which the coal constitutes,

about 10 weight percent of the mixture.

6. Method of claim 4 in which the coal constitutes about 20 weight percent of the mixture.

7. Method of claim 4 in which the coal is ground to a particle size of about percent finer than 200 mesh.

8. Method of claim 4 in which the heating temperature is about 315 C. and the heating time is 1 hour.

9. A binder and surface coating material prepared according to the method of claim 4.

10. A road building composition comprising a mixture of (1) an aggregate consisting of a material from the group consisting of crushed stone and crushed slag and (2) a binder prepared according to the method of claim 4.

11. Composition of claim 10 in which the binder comprises about 9 percent of the composition.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 1955 Canada.

1902 Great Britain. 1896 Great Britain. 1930 Great Britain. 1930 Great Britain. 1931 Great Britain.

OTHER REFERENCES 10 Asphalts and Allied Substances by Abraham, 5 ed., V01. 1, pages 468 and 531, published by D. Van Nostrand Co., New York, N.Y.

Asphalts and Allied Substances by Abraham, 5 ed., vol. I

15 1, pages 547-548, and 646, and vol. 2, page 1649, published by D. Van Nostrand Co., New York, N.Y.

FRANK L. ABBOTT, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

20 J. E. MURTAGH, Assistant Examiner. 

4. A METHOD FOR PREPARING A BINDER AND SURFACE COATING MATERIAL COMPOSED OF AN INSOLUBLE PARTICULATE BITUMINOUS COAL RESIDUE DISPERSED IN A SOLUTION OF BITUMINOUS COAL CONSTITUENTS AND PETROLEUM ASPHALT COMPRISING (A) INTIMATELY MIXING PETROLEUM ASPHALT WITH A FINELY DIVIDED BITUMINOUS COAL, THE COAL BEING ADDED IN AN AMOUNT UP TO ABOUT 20% BY WEIGHT OF THE TOTAL MIXTURE; (B) HEATING THE MIXTURE AT A TEMPERATURE OF FROM ABOUT 250*C. TO ABOUT 450*C. FOR FROM ABOUT 1/2 HOURS TO ABOUT 4 HOURS, THEREBY FORMING A DISPERSION OF INSOLUBLE BITUMINOUS COAL RESIDUE IN A SOLUTION COMPOSED OF (1) THE PETROLEUM ASPHALT AND (2) CONSTITUENTS OF THE BITUMINOUS COAL. 